1. Field of the Invention
The present invention relates generally to paint systems for vehicles and, more specifically, to a method of adaptively controlling a paint system for painting bodies of vehicles.
2. Description of the Related Art
The application of paint to a body of a vehicle is a sensitive process. The quality, durability and color matching of the paint are critical in producing a high quality product, and therefore require significant quality control efforts. A paint system is used to apply the paint to the vehicle bodies. The thickness of the film build measured from the vehicle body is the output of the paint system. However, the film thickness of the paint may vary with location due to geometric differences of the vehicle body. Also, there are significant delays between applying the paint, and obtaining the measured paint thickness, due to the time it takes for the paint to cure. The relationship between settings of the paint system and the measured paint thickness on the vehicle body is unclear and complicated. Those who have operated the paint system for a long time still have difficulty to conclude some clear rules to relate the inputs to the outputs of the paint system, e.g., the parameters of a set of paint applicators and the paint film thickness measured in the locations affected by these applicators.
As a result, it is desirable to provide an automatic control system for controlling the paint system. It is also desirable to provide a control method that incorporates adaptive learning and optimization in a closed loop paint system to control paint thickness in painting of vehicle bodies. It is further desirable to provide a method of adaptively controlling a paint system for painting vehicle bodies. It is still further desirable to provide an adaptive paint system control with intelligent resetting of initial conditions for painting vehicle bodies.
Accordingly, the present invention is a method of adaptively controlling a paint system for measuring paint film thickness of a painted body for a vehicle. The method includes the steps of obtaining an estimated Jacobian that identifies characteristics of the paint system and using the estimated Jacobian to determine control parameters to be implemented for the next vehicle body to be painted in the paint system. The method also includes the steps of storing a database of appropriate initial conditions that resulted in satisfactory transient response in a rule-base and using the rule-base at start-up of the paint system or if the paint system fails to be satisfactorily controlled.
One advantage of the present invention is that a method is provided of adaptively controlling a paint system to achieve uniform and consistent paint film thickness, thereby improving paint quality and reducing paint usage. Yet another advantage of the present invention is that the method incorporates intelligence for dealing with initial conditions and default settings. Still another advantage of the present invention is that the method replaces covariance resetting by using a rule-base, which plays the role of an associative memory, thereby improving transient behavior. A further advantage of the present invention is that the use of measurable but non-controllable environmental variables as an input to the rule-base determines xe2x80x9cacceptablexe2x80x9d initial conditions. Yet a further advantage of the present invention is that the method uses the concept of a Smith predictor to resolve transportation/measurement delays in a static paint system.
Other features and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.